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Abstract:
Using ICESat-2 ATL13 inland water products, and MODIS imagery, we compute water level variations from various lakes and reservoirs as well as water extent changes. The conversion of the ellipsoidal height into orthometric height requires an accurate geoid model. We show how recent geoid models can improve water level estimates than the classical EGM2008 used in the ATL13 products. We validate our water level estimates with available radar altimetry products and in-situ measurements. Using these two datasets, we derive volume changes. In addition, we derive corresponding mass variations of these water bodies using GRACE and GRACE Follow-On global mascon solutions from NASA GSFC. We show a good agreement between the water volume changes computed from ICESat-2 and MODIS and the mass changes deduced from space gravity missions. The main limitation of the gravimetry products is due to the spatial resolution of the GRACE & GRACE-FO solutions, and the quality of the hydrology models used to correct for the other continental water storage components, e.g. soil moisture and snow.As an independent validation, we compute surface displacements due to the lake/reservoir loading process, and compare them to available GNSS observations.
